The names of four Massachusetts police officers who died in the line of duty are among more than 250 that will be added to the National Law Enforcement Officers Memorial in Washington.

The dedication ceremony and a candlelight vigil are scheduled for Friday at the memorial on the National Mall.

Of the 252 officers added to the memorial this year, 123 died in 2015. The other 129 had died previously but were not documented.

The Massachusetts names being dedicated are Boston officer Jose Maceira, who died in 1977; Lynn officer George Crowell, who died in 1875; Peabody officer Edward Scott Johansen, who died in 1977; and Saugus Officer Phillip Pitts, who died in 1889.

With the addition of 252 names, the memorial will have nearly 21,000 names.